A hearty second for being in a room with a living breathing person. If that's absolutely impossible to do, I would suggest looking into skype lessons over watching static videos. If you hit a snag or if something isn't making sense to you, with skype lessons you, at the very least, have the opportunity to do some back and forth with the living breathing person at the other end of the interwebs. All any video can do is show you the same thing, the same way, over and over.
And even though bass guitar is not as physical an instrument as upright, I have to reiterate that in almost every single lesson I've had, my teacher was able to illustrate, either by taking the instrument out of my hands or manipulating my stance or posture or whatever, his point in a matter of seconds things that would be impossible (or at least extremely difficult and time consuming) to impart by typing or talking.

I have to agree with Ed Fuqua, although you can learn a lot from online videos, nothing beats a real human being who sees your mistakes and points them out in order to correct them. Especially for a beginner.

Thanks for the links guys. However, I'd definitely agree that there's no substitute for a real, live teacher. For a beginner it's a must. That said, you can have terrible, live teachers just as you can have terrible online advice. Although it has to be said that a 'good teacher' can be very much in the eye of the beholder. Some of my favourite teachers at university were hated by others and we all had different opinions on them. This all depended on the musicians styles and interests. Some of us just didn't get on with certain methods and content.

I think it also depends what your goals are. Some guys just want to play for a laidback hobby and in a local band. If you took up bass because you love Cliff Burton and just want to be able to play a few Metallica tunes in your spare time it can actually be frustrating to get a teacher that wants to ram jazz harmony and reading down your throat in the manner of a Jeff Berlin type. Some teacher's have got a set idea of 'what you must learn to be a proper bass player' and that can just annoy students who'll either just go somewhere else (another teacher or online) or put them off playing altogether (if they're really touchy!). That might seem a bit of an exaggeration but I've known loads of beginner players who've complained to me about not being able to relate to certain teachers who I considered great players and, for the most part, great teachers. It's easy to blame the student for not wanting to put the time and effort in but some people just want to have a bit of fun with the instrument and don't want to spend hours working on it.

So from that perspective I'd say that online tips and lessons can be quite valuable to someone who might find it really difficult to find the right teacher or be struggling with really getting into playing after mastering the basics. Also, some players live out in the middle of nowhere. Even in somewhere quite over populated like England, it's quite possible to find yourself in a village completely devoid of bass teachers, players or any musicians at all. For those people, online lessons can be a handy way of picking up tips and piecing it all together by themselves.

That said, if you have any aspirations of being a professional musician, learning jazz improvisation, harmony, aural, sight reading or any other aspects of music that require dedicated long term practice then I'd say get a live teacher. As someone that produces online content and teaches both on skype and in person, I'd definitely say that live, hands on teaching is the easiest and best way in terms of adapting to the student, which in turn speeds up the learning process tenfold. Even little things like being able to modify a students hand position by a fraction of an inch and improve the execution of a certain line is absolutely invaluable. If you can afford it and you have access to a teacher then go for it.

Thank-you Mark for your post, a very good perspective. My problem has been finding a good teacher (good for me, that is). I am gravitating towards on-line lessons because there just aren't any good teachers that I can find.

My problems are:

-I'm an adult (over 50), and don't want to play Justin Beiber songs. Every single teacher has been a twenty-something or younger. No offence to that age group, but knowing how to play bass does not = knowing how to teach bass.
-none of the teachers I've had ever bothered to ask me what my experience was. At the first lesson they just asked me what I wanted to learn (ie: "Do you want to learn any songs of just some scales?"
- There was never any "structure" to the lessons. Some were like a "jam" session. I just became frustrated and tried to find another teacher.
-none of the teachers ever provided instruction to me on technique.

I guess what I'm saying is that all the bass instruction near me seems geared to young kids who are beginners. In fact, some of the teachers were guitar players who happened to teach bass as well.